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IMAGE INTERPRETATION · THYROID AND PARATHYROID

Parathyroid Adenoma on Dual-Phase Sestamibi Scan

Tc-99m sestamibi parathyroid scintigraphy — dual-phase imaging
Tc-99m sestamibi parathyroid scintigraphy — dual-phase imaging

CC BY-SA 4.0 · Sincefalastrum / Wikimedia Commons · source file

Question

Tc-99m sestamibi dual-phase parathyroid scintigraphy is performed in a patient with primary hyperparathyroidism (elevated PTH and calcium). Early images show uptake in both the thyroid and a right inferior parathyroid region; delayed images (2 hours) show PERSISTENT uptake in the right inferior parathyroid region with washout from the thyroid. This pattern is MOST consistent with:

  1. ANormal parathyroid glands
  2. BThyroid adenoma
  3. CParathyroid carcinoma — always shows washout
  4. DRight inferior parathyroid adenoma — persistent sestamibi retention on delayed images indicates hyperfunctioning parathyroid tissue
Show the answer and explanation

D. Right inferior parathyroid adenoma — persistent sestamibi retention on delayed images indicates hyperfunctioning parathyroid tissue

Tc-99m sestamibi dual-phase parathyroid imaging exploits differential washout kinetics: normal thyroid tissue and normal parathyroid glands wash out sestamibi quickly, while hyperfunctioning parathyroid adenomas (which have abundant mitochondria from hyperplastic chief cells) RETAIN sestamibi on delayed images. The characteristic pattern of persistent focal uptake on 2-hour delayed images (with thyroid washout) localizes the parathyroid adenoma. Subtraction technique (Tc-99m sestamibi minus Tc-99m pertechnetate) further improves localization. SPECT/CT improves 3D localization for surgical planning. Sensitivity for single adenoma is ~85–90%; lower for hyperplasia or double adenomas.

More thyroid and parathyroid images

Thyroid scan — diffusely enlarged gland with homogeneously increased uptake, no discrete nodulesGraves’ Disease on Thyroid Scan Thyroid scintigraphy following ethanol injection into a thyroid noduleHot Thyroid Nodule: Autonomous Function Sequential I-123 total-body scintiscans over timeWhy I-123 Is Used for Diagnostic Thyroid Imaging Sequential I-123 whole body scan seriesI-131 vs I-123 for Post-Thyroidectomy Whole-Body Scans Thyroid scintigraphy — cold noduleCold Thyroid Nodule: The Next Step I-123 scan showing midline neck and sublingual uptakeLingual Thyroid on I-123 Scan
← Thyroid Stunning After Diagnostic I-131Graves’ Disease on Thyroid Scan →

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